Re: [mpls] Clarification on the motivation of draft-xu-spring-islands-connection-over-ip-05

Xuxiaohu <> Tue, 12 April 2016 10:15 UTC

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From: Xuxiaohu <>
To: "Carlos Pignataro (cpignata)" <>
Thread-Topic: [mpls] Clarification on the motivation of draft-xu-spring-islands-connection-over-ip-05
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Subject: Re: [mpls] Clarification on the motivation of draft-xu-spring-islands-connection-over-ip-05
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From: Carlos Pignataro (cpignata) []
Sent: Tuesday, April 12, 2016 8:23 AM
To: Xuxiaohu
Cc: Eric C Rosen;;
Subject: Re: [mpls] Clarification on the motivation of draft-xu-spring-islands-connection-over-ip-05

On Apr 7, 2016, at 6:39 PM, Xuxiaohu <<>> wrote:

On 4/6/2016 11:37 AM, Xuxiaohu wrote:

The situation in MPLS-SR is a little bit complex since the outgoing label for a given /32 or /128 prefix FEC could be learnt either from the IGP next-hop of that FEC or the originator of that FEC due to the IGP flooding property. In the former case, the IGP next-hop for a given FEC is taken as the next-hop of the received MPLS packet belonging to that FEC; in the latter case, the originator of that FEC is taken as the next-hop of the MPLS packet belonging to that FEC ... the latter case belongs to the "remote label distribution peer" case as defined in RFC3031

I don't believe this is correct.  In SR, the fact that label L was
advertised by node N does not imply that a packet with L at the top of
the stack needs to be tunneled to N.  In the typical case, the packet

[Xiaohu] The FEC associated the above label L is the /32 or 128/ prefix of node N. When the IGP next-hop towards that FEC is a non-MPLS node, the LSR receiving the above MPLS packet with top label of L is desired to forward that MPLS packet towards node N via an IP-based tunnel. In this case, the node N is the remote peer for that FEC.

Is this really a “remote label distribution peer”? Or a local one by way of the forwarding adjacency of an IP Tunnel as a logical MPLS-enabled interface (towards N or bypassing the old router)?

[Xiaohu] what’s the difference between the above two?

Best regards,


— Carlos.

Best regards,